Sensing apparatus

ABSTRACT

A sensing device is disclosed. The sensing device comprises: a first electrode layer, a second electrode layer, which are separated by a dielectric layer; and through holes penetrating through the first electrode layer, the second electrode layer and the dielectric layer.

CROSS-REFERENCES

The present disclosure claims priority of Chinese Patent Application No.201410385603.8 entitled “Sensing Apparatus” filed on Aug. 7, 2014, whichis incorporated herein by reference in its entirety.

TECHNICAL FIELD

The disclosure generally relates to electrochemical detection, and morespecifically, to a sensing device, such as an electrochemical biosensor.

BACKGROUND

An electrochemical biosensor comprises a biological sensitive elementand an electrochemical sensor. The biological sensitive elementcomprises early enzyme catalyst electrode, and later DNA, antigen,antibody, animalcule, and animal and plant tissues. Performance of suchsensors are continuously improved by various modern biologicaltechniques and chemical modification techniques.

In conventional electrochemical sensors as illustrated in FIG. 5,detecting electrodes 506-1, 506-2 are generally fabricated on a siliconsubstrate or other substrates 502. Probe molecules, indicated by Y-typesymbols in the drawing, may be attached to electrodes 506-1, 506-2. Whenfluid samples flow over the channel defined by the substrate 502 and thecover plate 504, as indicated by the horizontal arrow in the drawing, abiochemical reaction may occur between the molecules to be detected inthe samples (as indicated by the circle in the drawing) and the probemolecules. Variation of charges/currents during the biochemical reaction(generally, redox reaction) may be detected by the electrodes 506-1 and506-2. Typically, the electrode may have a structure of anInterdigitated microelectrodes Array (IDA). In such a case, two adjacentelectrodes, which can be used as an oxidation electrode and a reductionelectrode, respectively, constitute a group of electrode pair and may beapplied with different bias voltages. The process may be cycled andreciprocated, and may be referred as redox cycling. As illustrated inFIG. 5, in a redox cycling, the reduction product (R) on the cathode506-2 arrives at the anode 506-1 via diffusion and is oxidized. Then,the oxidation product (O) diffuses to the cathode and is reduced, andfinally the cycling is completed.

In the redox cycling, the path along which the reaction products diffuseand the time for the diffusion depend on the distance between thecathode 506-2 and the anode 506-1. The efficiency of the redox cyclingcan be improved by decreasing the spacing between adjacent electrodes,so as to increase the electrochemical detecting signals. Quantitatively,the steady-state current I_(limiting) in the redox cycling reaction canbe derived by:

$I_{limiting} = {{nFC}_{spe}{{Dmb}\left\lbrack {{0.637\mspace{11mu} \ln \frac{2.55\left( {w + g} \right)}{g}} - {0.19\left( \frac{g}{w + g} \right)^{2}}} \right\rbrack}}$

wherein g is the spacing between the adjacent electrodes, w is the widthof the electrode, m is the number of the Interdigitated electrode pairs,b is the length of the electrode, F is the Faraday constant, n is thenumber of the transferred electrons in the redox reaction, C_(spe) isthe concentration of the redox molecules, and D is the diffusioncoefficient of the redox molecules. According to the computation for therelationship between the steady-state current and the spacing of theinterdigitated electrode pairs in a typical experimental condition, thesteady-state current may decrease rapidly when the spacing is largerthan several microns.

In order to make full use of the characteristics of the redox cyclingand to increase the detecting current as large as possible, electrodesin micron or even nanometer scale are generally employed, and thespacing between electrodes are reduced as small as possible. Inconventional methods, the spacing between electrodes in nanometer scaleare fabricated by improving micro-nano fabricating process, for example,by deep ultraviolet lithography or electron beam lithography. However,the process difficulty and cost for fabricating nano-scale electrodesare increasing enormously with the scaling of the element. If electronbeam lithography is employed, current nano-scale electrodes may have adimension of about several nanometers, and long exposure time isrequired, which lead to lower yield.

Furthermore, in such an electrochemical detecting device, the moleculesto be detected are transported in a flow-over mode, as illustrated inFIG. 5. Specifically, the molecules to be detected have to diffuse inthe vicinity of the probe molecules in order to have a binding reaction.In a laminar flow state in micro-scale, binding efficiency of themolecules to be detected and the probe molecules is restricted.

SUMMARY OF INVENTION

An object of the present disclosure is to provide, among others, asensing device, which can efficiently detect targeting particles, suchas chemical and/or biological molecules.

According to embodiments of the present disclosure, a sensing device isprovided. The sensing device comprises: a first electrode layer, asecond electrode layer, which are separated by a dielectric layer; andthrough holes penetrating through the first electrode layer, the secondelectrode layer and the dielectric layer.

In the sensing device- according to embodiments of the presentdisclosure, spacings between electrodes in, for example, several toseveral tens of nanometers, are naturally formed by means of thedielectric layer between two electrode layers (which constitute athree-dimensional electrode configuration) without the complicated andexpensive electron beam lithography process.

Furthermore, in conventional electrochemical sensors (as shown in FIG.5), molecules to be detected flow over the device (electrode). In a casewhere laminar-flow in micro-scale occurs, the reaction of molecules tobe detected with probe molecules is mainly controlled by the diffusionspeed of the molecules to be detected, which may lead to lower detectingspeed and worse sensitivity. According to embodiments of the presentdisclosure, a novel micro/nano through hole structure is provided.Electrodes are disposed in different levels and fluid samples flowthrough the through holes, which greatly enhances diffusion efficiencyof the molecules to be detected and probability with which the probemolecules react, and improves sensor sensitivity.

DESCRIPTION OF DRAWINGS

The above and other objects, features, and advantages of the presentdisclosure will become more apparent from the following descriptions ofembodiments thereof with reference to attached drawings, in which:

FIG. 1 schematically illustrates a perspective view of a sensing deviceaccording to an embodiment of the present disclosure;

FIG. 2 schematically illustrates a cross-sectional view of a sensingdevice according to another embodiment of the present disclosure;

FIG. 3 schematically illustrates a cross-sectional view of a sensingdevice according to a further embodiment of the present disclosure;

FIG. 4 schematically illustrates a cross-sectional view of a sensingdevice according to a still further embodiment of the presentdisclosure; and

FIG. 5 illustrates a schematic view of an electrochemical sensor inrelated art.

DETAILED DESCRIPTION

Hereinafter, descriptions are given for embodiments of the presentdisclosure with reference to the attached drawings. However, it is to beunderstood that these descriptions are illustrative and not intended tolimit the present disclosure. Further, in the following, knownstructures and technology are not described to avoid obscuring conceptsof the present disclosure unnecessarily.

In the drawings, various structures according to embodiments of thepresent disclosure are schematically shown. However, they are not drawnto scale, and some features may be enlarged while some features may beomitted for sake of clarity. Moreover, shapes and relative sizes andpositions of regions and layers shown in the drawings are onlyillustrative, and deviations may occur due to manufacture tolerances andtechnique limitations in practice. Those skilled in the art can alsodevise regions/layers of other different shapes, sizes, and relativepositions as desired.

In the context of the present disclosure, when a layer/element isrecited as being “on” a further layer/element, the layer/element can bedisposed directly on the further layer/element, or otherwise there maybe an intervening layer/element interposed therebetween. Further, if alayer/element is “on” a further layer/element in an orientation, thenthe layer/element can be “under” the further layer/element when theorientation is turned.

According to embodiments of the present disclosure, a sensing device isprovided to detect targeting particles in samples, such as chemicaland/or biological molecules. The sensing device comprises a firstelectrode layer, a second electrode layer, which are separated by adielectric layer, and through holes penetrating through the firstelectrode layer, the second electrode layer and the dielectric layer. Athrough hole array may be formed in a cribriform structure.

The sandwich structure of the first and second electrode layers and thedielectric layer can be disposed on one side of a substrate, and thethrough holes may penetrate through the substrate. Optionally, a furthersandwich structure of a further first electrode layer, a further secondelectrode layer and a further dielectric layer can also be disposed onthe opposite side of the substrate. And the through holes may alsopenetrate through the further sandwich structure.

The through holes may have various types as appreciate (for example, foreasy manufacturing), such as a substantially circular type. The throughholes in the array may have the same or different types, and therespective through holes may have the same or different dimensions. Thethrough holes may perpendicularly penetrate through the sandwichstructure of the first electrode layer, the second electrode layer andthe dielectric layer (and optionally, the substrate thereunder). Eachthrough hole may have the same or different dimension in the first andsecond electrode layers.

According to embodiments of the present disclosure, the sensing devicemay comprise a microfluidic chip which is configured to introduce fluidsamples into the device such that the samples can flow through thethrough holes.

Such sensing devices can be used as electrochemical biosensors.

The technology of the present disclosure can be implemented in variousways, some of which are exemplified in the following with reference tothe drawings.

FIG. 1 schematically illustrates a perspective view of a sensing deviceaccording to an embodiment of the present disclosure.

As shown in FIG. 1, the sensing device 1000 according to the embodimentcan comprise a substrate 1002. For example, the substrate 1002 maycomprise at least one of semiconductor materials, such as silicon,inorganic materials, such as glass and quartz, and polymers, such aspolymethyl methacrylate and polycarbonate.

A first electrode layer 1004, a dielectric layer 1006 and a secondelectrode layer 1008 are sequentially formed on the substrate 1002.Optionally, a passivation layer 1010 may be formed on the secondelectrode layer 1008 to protect the respective layers thereunder. Therespective layers can be formed on the substrate 1002 by, for example,deposition or evaporation. The first electrode layer 1004 and the secondelectrode layer 1008 may comprise appropriate conducting materials, forexample, metals, such as Au, and may have a thickness of about severalto hundreds of nanometers. In order to enhance adhesion between theelectrode layer and the substrate 1002 or between the electrode layerand the dielectric layer 1006, a transition layer may be formed betweenthe electrode layer and the substrate 1002 and/or between the electrodelayer and the dielectric layer 1006. The transition layer may compriseconducting materials as appropriate, for example, metals, such as Ti,Cr, etc., and may have a thickness of about several to several tens ofnanometers. The dielectric layer 1006 comprises dielectric materials asappropriate, for example, silicon oxide, silicon nitride, etc., and mayhave a thickness of about several to several tens of nanometers. Thepassivation layer 1008 may comprise silicon oxide, silicon nitride orother polymers, and may have a thickness of about several to hundreds ofnanometers.

It should be noted that, the substrate beneath the sandwich structure ofthe electrode layers and the dielectric layer and the passivation layeron the sandwich structure are schematically shown in FIG. 1. However,they are optional. In some applications, the substrate and/or thepassivation layer may be even omitted.

In the sandwich structure, through holes 1012 can be formed to penetratethrough the sandwich structure on opposite sides (in the drawings, upperand lower sides) by, for example, an etching process. For example, thethrough holes 1012 may have a circular type and may have a diameter ofabout 100 nm-500 μm. In a case where the substrate 1002 and/or thepassivation layer 1010 are formed, the through holes 1012 also penetratethrough the substrate 1002 and/or the passivation layer 1010. The fluidcan flow through the through holes from one side of the device (forexample, the upper side in FIG. 1) to the other side (for example, thelower side in FIG. 1), such that the fluid can flow through the firstand second electrode layers, and electrochemical detecting is achievedwith high efficiency.

Though an array of 4×4 through holes is shown in FIG. 1, the presentdisclosure is not limited thereto. There may be more or less throughholes. Further, the array in FIG. 1 is an array having a regular squareshape. However, the present disclosure is not limited thereto. Thethrough holes may be disposed in other regular or irregular patterns.The shapes of the through holes are not limited to the regularcolumniform shown in the drawings. The through holes may have any othershape which is suited for manufacturing, and may comprise variations inshape caused by manufacturing tolerance, process limitation, etc.

Further, in the example in FIG. 1, the sandwich structure of theelectrode layers and the dielectric layer is only formed on one side(upper side in FIG. 1) of the substrate 1002. However, the presentdisclosure is not limited thereto. For example, another sandwichstructure of the electrode layers and the dielectric layer can be formedon the opposite side (lower side in FIG. 1) of the substrate 1002. Theelectrode layers and the dielectric layer in the another sandwichstructure may have the same or different configuration as that of theabove sandwich structure.

FIG. 2 schematically illustrates a cross-sectional view of a sensingdevice according to another embodiment of the present disclosure.

As shown in FIG. 2, the sensing device 2000 according to the embodimentcan comprise a substrate 2002. A first electrode layer 2004, adielectric layer 2006, a second electrode layer 2008 and a passivationlayer 2010 are sequentially formed on the substrate 2002. Description ofthe configuration of the substrate and these layers can be referred toexplanation given with reference to FIG. 1.

The sensing device 2000 can also comprise a through hole (2012-1 and2012-2) penetrating through the substrate 2002 and respective layersthereon. In the embodiment, the through hole has a dimension in thesecond electrode layer 2008 (2012-4) different (in this embodiment,larger) from that in the first electrode layer 2004 (2012-2). Forexample, such a through hole can be manufactured as follows.Specifically, the passivation layer 2010, the second electrode layer2008 and the dielectric layer 2006 are sequentially etched by, forexample, Reactive Ion Etching (RIE) by means of a first photomask. Thefirst photomask can define an opening with a relative large size. Next,the first electrode layer 2004 and the substrate 2002 are sequentiallyetched by means of a second photomask. The second photomask can definean opening with a relative small size.

The probe molecules, for example, antibody protein, as indicated byY-type symbols in the drawings, can be attached to surfaces of thethrough holes exposed in the first electrode layer 2004 and the secondelectrode layer 2008. Electrical signals, such as direct or alternatingcurrent signals, can be applied to the first electrode layer 2004 andthe second electrode layer 2008. Those skilled in the art can conceivevarious means to form connections such as wirings to apply electricalsignals to the first electrode layer 2004 and the second electrode layer2008. When the fluid samples flow through the through hole along adirection indicated by the arrow in the drawing, the molecules to bedetected in the samples (indicated by the circular symbol in thedrawing) may react with the probe molecules, so as to achieve detectionof the molecules to be detected. For particular molecules to bedetected, it is apparent for selection of probe molecules for thoseskilled in the art.

It should be noted that only a single through hole (2012-1 and 2012-2)is shown in FIG. 2 for the sake of convenience. However, the presentdisclosure is not limited thereto. There may exist more through holes.

FIG. 3 schematically illustrates a cross-sectional view of a sensingdevice according to a further embodiment of the present disclosure. Thesensing device 3000 is substantially the same as the sensing device 2000in FIG. 2 except that the through holes have different shapes.

As shown in FIG. 3, the sensing device 3000 according to the embodimentcan comprise a substrate 3002. A first electrode layer 3004, adielectric layer 3006, a second electrode layer 3008 and a passivationlayer 3010 are sequentially formed on the substrate 3002. Description ofthe configuration of the substrate and these layers can be referred toexplanation given with reference to FIG. 1.

The sensing device 3000 can also comprise a through hole penetratingthrough the substrate 3002 and respective layers thereon. In theembodiment, the through hole have a dimension in the second electrodelayer 3008 substantially the same as that in the first electrode layer3004. Specially, in the embodiment, the through hole has cross sectionsin substantially the same size to penetrate through the respectivelayers. For example, such a through hole can be manufactured as follows.Specifically, the passivation layer 3010, the second electrode layer3008, the dielectric layer 3006, the first electrode layer 3004 and thesubstrate 3002 are sequentially etched by, for example, Reactive IonEtching (RIE) by means of the same photomask.

The probe molecules, for example, antibody protein, as indicated byY-type symbols in the drawings, can be attached to surfaces of thethrough hole exposed in the first electrode layer 3004 and the secondelectrode layer 308. Electrical signals, such as direct or alternatingcurrent signals, can be applied to the first electrode layer 3004 andthe second electrode layer 3008. When the fluid samples flow through thethrough hole along a direction indicated by the arrow in the drawing,the molecules to be detected in the samples (indicated by the circularsymbol in the drawing) may react with the probe molecules, so as toachieve detection of molecules to be detected.

FIG. 4 schematically illustrates a cross-sectional view of a sensingdevice according to a still further embodiment of the presentdisclosure.

As shown in FIG. 4, the sensing device can comprise a substrate 4002. Afirst electrode layer 4004, a dielectric layer 4006, a second electrodelayer 4008 and a passivation layer 4010 are sequentially formed on thesubstrate 4002. The sensing device can also comprise through holespenetrating through the substrate 4002 and respective layers thereon.Description of the configuration of the substrate and these layers canbe referred to explanation given with reference to FIGS. 1-3.

The device can also comprise a microfluidic chip 4014. The microfluidicchip 4014 can comprise an inlet 4016 for introducing fluid samplescontaining molecules to be detected into the device such that the fluidsample can flow through the through holes 4012. Though only one inletfor sample loading is shown in FIG. 4, the present disclosure is notlimited thereto. The microfluidic chip can comprise more inlets.

The microfluidic chip can precisely control and manipulate fluid inmicro-scale. For example, the microfluidic chip may be manufactured oftransparent polymers, such as Polymethylmethacrylate (PMMA),Polycarbonate (PC), Polydimethylsiloxane (PDMS), etc., and may havemicro-structures, such as micro-channels, micro-cavities, etc.,manufactured by microfabrication techniques. The micro-structures haveat least one dimension in micro-scale among scales such as length,width, height, etc. A closed channel can be formed by bonding themicrofluidic chip with structures thereunder or by applying pressure, soas to transport fluid.

Various features are described in different embodiments in the abovedescriptions. However, it is not implied that these features cannot becombined advantageously.

In the above, embodiments of the present disclosure are described.However, such embodiments are given for illustrative only, rather thanlimiting the scope of the present disclosure. The scope of the presentdisclosure is defined by appended claims and equivalents thereof.Without departing from the scope of the present disclosure, thoseskilled in the-art can make various alternations and modifications whichfall within the scope of the present disclosure.

1. A sensing device, comprising: a first electrode layer and a secondelectrode layer, which are separated by a dielectric layer; and throughholes penetrating through the first electrode layer, the secondelectrode layer and the dielectric layer.
 2. The sensing device of claim1, further comprising: a substrate, wherein the first electrode layer,the dielectric layer and the second electrode layer are sequentiallyformed on one side of the substrate, and wherein the through holespenetrate through the substrate.
 3. The sensing device of claim 1,wherein the through holes have a dimension in the first electrode layerdifferent from that in the second electrode layer.
 4. The sensing deviceof claim 3, wherein the through holes have a dimension in the dielectriclayer substantially the same as that in the second electrode layer. 5.The sensing device of claim 1, wherein the through holes have adimension in the first electrode layer substantially the same as that inthe second electrode layer.
 6. The sensing device of claim 5, whereinthe through holes have a dimension in the dielectric layer substantiallythe same as that in the first and second electrode layers.
 7. Thesensing device of claim 1, wherein an array of multiple through holes isformed.
 8. The sensing device of claim 1, wherein the through holes havea circular shape, and have a diameter of about 100 nm-500 μm.
 9. Thesensing device of claim 2, further comprising: a further first electrodelayer, a further dielectric layer and a further second electrode layersequentially formed on the other side opposite to the one side of thesubstrate, wherein the through holes penetrate through the further firstelectrode, the further dielectric layer and the further second electrodelayer.
 10. The sensing device of the claim 1, further comprising: amicrofluidic chip, which is configured to introduce fluid samples suchthat the fluid samples flow through the through holes.